This invention relates to tamper sensors for bolts and screws, and more particularly to the arrangement of such a sensing device and a circuit for sensing tampering and reporting an alarm.
Generally, in order to maintain the integrity of a housing cover installed on a base, various mechanical arrangements may be used for prevention of tampering and theft. However, there are practical limits to how secure a mechanical housing may be constructed so as to resist tampering. Stronger materials may be chosen for screws, bolts, and other fasteners, or the cover may be made of a material having greater strength. But, in some way, structural integrity may be violated, and this condition needs to be sensed and reported.
There are other situations in which it is desirable to have a housing cover removably attached to a base, as by bolts and screws, to allow authorized removal of the cover. In this situation it is often desirable to prevent tampering with, or the unauthorized removal of, the cover. Up until this time, there have been no satisfactory systems for preventing physical tampering, and there are no electrical tamper sensing systems for sensing tampering and reporting an alarm while tampering is in progress. Further, there are no satisfactory electrical tamper sensors responsive to the simple removal of bolts and screws for actuating an alarm.
The prior U.S. patent literature shows U.S. Pat. Nos. 4,092,641 to Billinghausen et al and 3,866,203 to Berns. The Billinghausen system is responsive to attempts to pilfer or tamper with condition detector structures, such as smoke detectors, intrusion detectors and the like. A switch apparatus incorporated with the enclosure completes a circuit and sounds an alarm. The Berns patent also discloses an audible signaling apparatus having a switch which is subject to actuation by physical movement of a lock housing. Other tamper sensing systems are known from U.S. Pat. Nos. 4,150,371 and 4,149,158.